The present invention relates to filtering devices that can be employed in clarifying nonaqueous carbonaceous liquids containing fine particles within slurries. It is particularly well adapted for use in clarifying carbonaceous liquid fuels such as those produced in the liquefaction of coal and other solid carbonaceous material.
One major problem in the development of coal liquefaction processes is the removal of fine solid particles following liquefaction. Rotary drum filtration has been employed, but its unfavorable economics have stimulated research into alternate techniques.
The settling of solids by the addition of a precipitating liquid, such as O-xylene, has been attempted but large volumes of promoter liquids are necessary. In addition, settling separations have not worked well for the final removal of fine particles or particles in colloidal dispersions.
In related prior processes, aqueous suspensions of fine particles have been subjected to forced-flow electrophoresis at low voltages to prevent the decomposition of water. Electrostatic precipitation of dust from air has been carried out at high electrical potentials, but these procedures are different and have not previously been applied to clarify liquids from slurries.